Caustic soda and chlorine are produced by the electrolysis of brine in a chlor-alkali plant. The electrolysis of brine produces 1.1 pounds of caustic for each pound of chlorine. The demand for caustic soda often is substantially less than that for chlorine. When this occurs there is a large requirement for caustic soda storage space, especially since the chlorine can be converted to ethylene dichloride which may in turn require large storage space when there is an unbalance in demand for chlorine and caustic. Another example of the requirement for large volume of storage space results in the cyclic marketing situation for anhydrous ammonia which is used as a direct application agricultural fertilizer at the time the soil is first prepared for planting. In this case the supply and demand for anhydrous ammonia are seldom in balance.
In any of the above cases and in other commerical production, especially in the oil and gas industries it is uneconomical to store large volumes of such products, for extended periods of time, which accumulate during the cyclic market conditions, in above ground tanks.
The liquefied petroleum gas (LPG) industry faced the problem of imbalance of supply and demand for LPG in the early 1950's with respect to propane and butane. The LPG industry resolved their problem by developing underground storage chambers in salt deposits via solution mining. This development allowed for balancing the supply and demand of propane and butane and this resulted in generating public confidence and a tremendous expansion of the LPG industry.